checkpoint progress on removing container_internals layer before
taking on container_trunc().
add a containerfd extend function for truncate.   can't do it in
as we don't have access to containerfd this->fd when accessed from
containerfs.
finish partial trunc() reorg...
get rid of old trunc code
retire container_internals.
Merge pull request #292 from chuckcranor/2.5dev

Builds with no issue and passes the regression suite as well.
Merge branch '2.5dev' of github.com:plfs/plfs-core

Conflicts:
	tools/plfs_flatten_index.cpp